What Reddy and Pogge
don't say:

a)  Even the people who run PPP say it is unreliable for poverty research (see
International Comparison Programme reports and UN correspondence)

and two implications which I seem to have identified of the flaw:

b)  Distortions in PPP as a measure of poverty make the results of poverty
comparisons using PPP highly suspect.   

(Examples:  "Assessing Aid" and "Growth, Globalisation and Poverty" from the WB.
  The second of these claims more poverty reduction in globalising countries). 
This can be deduced from the ICP documents  -  and common sense  -   without
using Reddy and Pogge's estimates.